Fuzzy Logic Controller: Choosing Membership Function
First I need to note that there is no prescribed/best way to choose the shape of membership function in fuzzy systems, that's the fuzziness in it. One could argue that the best way is to ask an expert in the field where you are going to apply your fuzzy solution but those are not always available.

With that said, fuzzy membership functions are used to describe the distribution of probabilities in real world for the variable you are trying to use in your fuzzy controller. That means you go out in the real world, you look at the system you are trying to control, you try your best to understand how it works and reacts to different outside changes and based on your findings you choose the shape that best fits. Or if you want you may call this process heuristic choice (something like that, I do not like theory very much).

On top of that you need to realize one important thing, the shape of membership function does not have big impact on the resulting controller behavior. The most influencing parts are the Fuzzy Rules and their inference methods you use in your controller, but that is a different topic. So no matter what you choose it will not make a big difference. 

Gaussian functions are most commonly used because of the character of the world we are living in. Many people argue that everything in the world has Gaussian distribution (everyone is entitled to their opinion). And the triangular functions are used because they are the simplest alternative that is somewhat similar to Gaussian function.

But if you absolutely need to chose the best one for your particular problem. There always are Simulation tools that exists precisely for this purpose. One of them is Matlab Simulink as you mentioned, but there are others if you don't like the price of the Matlab.

My suggestion is, go with your gut, test it in safe environment and if it works then deploy it to the real world.